Description:

Stubs out a new messenger and its views. Passes the messenger name,
either CamelCased or under_scored, and an optional list of messengers as arguments.

This generates a messenger class in app/messengers and invokes your template
engine and test framework generators.

Example:

rails generate messenger Account registerd_notify

creates a Account messenger class, views, and test:
    Messenger:  app/messengers/account_messenger.rb
    Views:      app/views/account_messengers/registerd_notify.text.erb